Deoxyhypusine hydroxylase is the enzyme that catalyzes the final step in the synthesis of hypusine, a unique post-translational modification essential for eukaryotic cell proliferation. Hypusine [Nε-(4-amino-2-hydroxybutyl)-lysine] occurs in a single cellular protein, eukaryotic translation initiation factor-5A(eIF-5A) (for reviews see Park et al., Trends Biochem. Sci. 18(12): 475–479 (1993); Park et al., Biol. Signals 6(3): 115–123 (1997); and Chen et al., Biol. Signals 6(3): 105–109 (1997)). It is formed in two enzymatic steps that occur immediately following translation of the eIF-5A precursor protein. In the first step, catalyzed by deoxyhypusine synthase, the intermediate deoxyhypusine is formed by nicotinamide adenine dinucleotide (NAD)-dependent transfer of the 4-aminobutyl moiety of the polyamine spermidine to the ε-amino group of a specific lysine residue in the eIF-5A precursor (Chen et al., FEBS Letters 229(2): 325–328 (1988); Murphey et al., J. Biol. Chem. 262(31): 15033–15036 (1987); and Wolff et al., J. Biol. Chem. 270(15): 8660–8666 (1995)). The second step involves hydroxylation of the side chain of this intermediate by deoxyhypusine hydroxylase (Park et al., J. Biol. Chem. 257(12): 7217–7222 (1982); and Abbruzzese et al., J. Biol. Chem. 261(7): 3085–3089 (1986)).
Prolyl 4-hydroxylase (procollagen-proline dioxygenase) is a non-heme iron enzyme that catalyzes hydroxylation of proline residues in protocollagen to trans-4-hydroxy-L-proline, and thereby promotes triple helix formation, collagen secretion and deposition into the extracellular matrix (for a review see Kivirikko et al., Adv. Enzymol. Relat. Areas Mol. Biol. 72: 325–398 (1998)). It has been reported to be inhibited by several metal chelators, including mimosine, deferiprone, 2,2′-dipyridyl and deferoxamine, in vitro, or in cultured cells (McCaffrey et al., J. Clin Invest. 95(2): 446–55 (1995); U.S. Pat. No. 6,046,219; Chvapil et al., Biochem. Pharmacol. 23(15): 2165–73 (1974); and Rosenbloom et al., FEBS Lett. 65(2): 246–50 (1976)).
While it is known in the art that mimosine, ciclopirox and deferiprone, all of which are inhibitors of deoxyhypusine hydroxylase, have been shown to inhibit cell cycle progression in late G1 in certain mammalian cells (Hanauske-Abel et al., Biochim. Biophys. Acta 1221(2): 115–24 (1994); Andrus et al., Biochem. Pharmacol. 55(11): 1807–18 (1998); Lalande et al., Exp. Cell. Res. 188(1): 117–21 (1990); and Hoffman et al., Cytometry 12(1): 26–32 (1991)), until now it has not been known whether inhibitors of deoxyhypusine hydroxylase can inhibit proliferation of cells of a non-vascularized intraepithelial neoplasia. Furthermore, while it is known in the art that mimosine can additionally inhibit prolyl 4-hydroxylase and collagen biosynthesis in human smooth muscle, causing arrest of capillary formation, until now it has not been known whether ciclopirox and derivatives thereof, as well as other inhibitors of prolyl 4-hydroxylase, can inhibit the formation of vascular channels in tissues.
It has now been discovered that proliferation of cells of a non-vascularized intraepithelial neoplasia can be inhibited. It also has been discovered that the formation of vascular channels in tissues can be inhibited. In view of these discoveries, the present invention seeks to provide a method of inhibiting proliferation of a cell of a non-vascularized intraepithelial neoplasia and a method of inhibiting the formation of vascular channels. These and other objects and advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.